[DRBD-user] Correct way to lvreduce a drbd volume

[Paul O'Rorke]

Hi list,

I have an LVM backed DRBD resource for a libvirt VM that I wish to 
reduce in size however neither lvresize nor resize2fs are working for me.

backing device for the volume is */dev/trk-kvm-02-vg/blmail* and is 
currently 300G and I want to bring it down to 30G.  My intended use for 
this server has changed.

    root at trk-kvm-02:~/scripts# lvs
       LV                VG            Attr       LSize Pool Origin
    Data%  Meta%  Move Log Cpy%Sync Convert
       [...]
       blmail            trk-kvm-02-vg -wi-a----- 300.00g
       [...]

I bring down the resource and try lvresize on /dev/trk-kvm-02-vg/blmail:

    root at trk-kvm-02:~/scripts# lvreduce --resizefs -L 30G
    /dev/trk-kvm-02-vg/blmail
    fsck from util-linux 2.27.1
    fsadm: Filesystem "drbd" on device
    "/dev/mapper/trk--kvm--02--vg-blmail" is not supported by this tool
       fsadm failed: 1
       Filesystem resize failed.

So I thought I'd use a hammer and resize the file system and dd it onto 
a new smaller LVM volume and recreate new drbd meta-data if needed:

    root at trk-kvm-02:~/scripts# resize2fs /dev/trk-kvm-02-vg/blmail 30G
    resize2fs 1.42.13 (17-May-2015)
    resize2fs: Bad magic number in super-block while trying to open
    /dev/trk-kvm-02-vg/blmail
    Couldn't find valid filesystem superblock.

I would seem to be barking up the wrong tree.  Can anyone point me in 
the right direction for documentation or suggest what is the right 
approach to reducing this volume?

please and thanks

-- 

*Paul O'Rorke*
*Tracker Software Products (Canada) Limited *
www.tracker-software.com <http://www.tracker-software.com/>
Tel: +1 (250) 324 1621
Fax: +1 (250) 324 1623

<http://www.tracker-software.com/>

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